Plans for new, faster supersonic civilian transport aircraft specify a fuselage made from a hybrid composite structures. The planned cruising speeds for these aircraft, well in excess of the speed of sound, will subject the fuselage for these aircraft to sustained high operating temperatures. Neither all metal nor all polymeric matrix composite structures are satisfactory for economical sustained use in transporting civilian passengers under these conditions. Designers have therefore turned to hybrid composite structures.
Hybrid composite structures generally include layers of metal, polymeric matrix composite, and honeycomb material bonded to one another in a sandwich type of arrangement. These types of structures can withstand sustained high operating temperatures and have a high strength-to-weight ratio, both of which are critical for high speed transport applications.
However, hybrid composite structures are difficult to manufacture. One of the largest contributors to this difficulty is the amount of manual labor required during fabrication. Present fabrication techniques for producing hybrid composite structures are similar to techniques used in producing conventional polymeric matrix composite structures. Specifically, the various layers in the structure are laid-up with one another on a lay-up mandrel in a laborious process. Typically, thereafter the entire structure is manually sealed in a vacuum bag and placed in an autoclave for consolidation, cure and bonding of the various layers to one another.
Additionally, integral, large scale parts can be difficult to manufacture from some types of hybrid composite structures. For example, hybrid composite structures formed from aramid polymeric matrix composite and aluminum, known as ARALL, usually require stretching as part of the manufacturing process. The stretching process creates difficulties when attempting to form integral, large scale parts that must conform to close manufacturing tolerances. As a practical matter, large parts formed from ARALL thus must include several smaller ARALL sections that fasten together to form the part. The same is also true for hybrid composite structures formed from glass polymeric matrix composite and aluminum, known as GLARE.
Automatic tape laying machines have reduced fabrication costs in conventional polymeric matrix composite structures. The tape laying machines automatically place layers of composite impregnated tape, rather than composite sheets, on a lay-up mandrel, a method which can significantly reduce labor costs for some parts.
However, present fabrication techniques for hybrid composite structures still rely upon manually placing the metal and honeycomb layers of the structure on a lay-up mandrel. When using exotic metal foils with anodized surfaces, manual contact with the anodized surfaces during fabrication must be prevented to avoid contamination. Thus, manual lay-up techniques are not satisfactory.